On 12/09/2018 17:24, Andy Lutomirski wrote: >> I think you can go a step further and exclude PKRU state from >> copy_kernel_to_fpregs altogether; you just use RDPKRU/WRPKRU. This also >> means you don't need to call __fpregs_* functions in write_pkru. >> >> > Except that the signal ABI has PKRU in the xstate. So we’d need to fake it or > do something special for signals.
The signal ABI is already special because it uses the non-compacted format. As long as copy_fpregs_to_sigframe includes the PKRU state (i.e. EDX:EAX=-1), and PKRU value is okay (which it is because it's switched eagerly), everything should work... Paolo
